mmg_233_2014_genetics_genomicsfandomcom-20200215-history
Horizontal Gene Transfer in Parasitic Nematodes
What is Horizontal Gene Transfer (HGT)? Horizontal gene transfer refers to any mechanism, other than traditional reproduction, that transfers DNA from one organism to another. For example, this accounts for antibiotic resistance in bacteria and the symbiosis between mitochondria and the human body. In the articles below, parasitic genes of a nematode were closely examined and found that one enzyme that this organism produces must have been aquired through HGT. Parasitic Nematodes and HGT What are Nematodes? Nematodes or roundworms are a diverse group of eukaryotic organisms that mostly live a parasitic lifestyle. They are found in many different environments including but not limited to: oceans, soil, mountains, deserts, and even the human body. The type of nematode that these two articles focus on is the group of nematodes that affect plants. How do Nematodes "kill" the plant? ''' Since most nematodes are parasitic, they do not fully kill the plant. They need that the nutrients that the plant supplies so that it can sustain its own life. So the plant does not die, but it is affected by having the nematode sucking nutrients away from it. the plant becomes less hardy and cannot grow as well if it did not have this parasite. Through evolution, the nematode has developed a certain strategy for feeding off of the host plant. It has a very elaborate feeding mechanism in its mouth called a "feeding spear" or stylet. This spear pierces the lining of the root of the plant and injects different enzymes such as cellulase into the plant. These enzymes degrade the plant material in that area and then the nematode sucks the nutrients back through the stylet. Nematodes are usually found in the roots of the plants since they are able to survive and flourish in the soil and not really above ground. '''HGT and Nematodes When horizontal gene transfer is mentioned, it is usually in respect to prokaryotes transferring between themselves. HGT is very common among prokaryotic species and not so common in eukaryotes. These two authors both looked at the enzyme of cellulase because it is very important to the nematode. They discovered that cellulase is an enzyme that is usually produced by microbes and not by eukaryotes. They do not know when this gene transfer occurred. But they both agree that not only where genes transferred, but whole sections of chromatin were transferred and not just a single gene. They both speculate that this happened a long time and more research needs to be put into this topic because it is very interesting. These articles were both published in the early 2000's and did not have the next generation sequencing technology needed to really look into these genomes they way they wanted to. One of the researchers stated that he wanted to find a way to perform a metagenomic analysis on the microbes in the soil and compare them to the nematodes. This extra information could help understand where these different digestive enzymes came from. Resources Horizontal Gene Transfer, Wikipedia, Retrieved 11/17/14. Cellulase, Wikipedia, Retrieved 11/17/14. "Nematode Parasitism Genes", Davis EL et. al, Annu Rev Phytopathol. 2000;38:365-396. PMID: 11701847 "Nematode Genome Evolution", Coghlan A., WormBook. 2005 Sep 7:1-15. PMID: 18050393 :